Visual Memory Research
The Genesis of Mnemonic Visual Systems 
Recurrent Dynamics in Excitable Media

Topic D10: The Subjective Radial Array

A  Global  Percept:   the   " Mandala " Template The Perkinje Rose.
The term "Mandala" is a tag used to identifying the subjectively-perceived rose-window geometry. After adaptation of both eyes to bright sunlight a subjective pattern soon appears in dark; it is seen as a radial figure of motile luminous blue nodes on a darker ground, and persists indefinitely and  with modulations.
  Adaptive  Transients
  Empirically demonstrable by visually cycling between red umbral light (Fig. 1) and darkness (Fig. 2), at seven-second intervals; adaptive-transients generate red/blue off-set  radial patterns whose salience increases to a maximum during each of the seven-second periods, and this effect is further enhanced by continued cycling.

After exposure to daylight a subjective pattern of oscillating clusters is commonly experienced in the dark.  This mandala, the master-template of radial pattern, reverberates throughout the visual hierarchy.    The cortical network oscillation is organized with  two settings tightly coupled to form locally  opponent  oscillators . (see E13, E15, and D11)
           Entoptically, the dynamical visual system appears as a polar network of pulse-coupled oscillators in a  radial lattice, in which unstable attractors can arise from dichoptic, asymmetric photic stimuli.   Synchronized oscillators (clusters) are activated resulting in apparent inter-ocular transfers or combinations. These  Mandala-oscillatory phenomena can be modified by changes in lighting, local or global ,.symmetric or dichoptic . 

    Dark Adapted .  The Mandala pattern is unscannable and appears as radially-symmetrical luminous nodes centered upon the foveolar fixation point, a polar geometry familiar to most cultures and depicted in the ancient "mandalas"; serving also as the nautical compass-rose.
The streams of signals emitted by these "luminous" nodes, estimated at between 5-10 Hz, are experienced on the dark as "the visual noise" of synchronized/ oscillating clusters.
 The local intensities are modifiable by cyclical sweeps of the Helmholtz bands (D11), by local perturbations,  and by asymmetric diffuse ambient light.                      

Pressure Effects. 

 The polar topography in umbral view may also be demonstrated by steady mechanical pressure on the eye.  (Fig 4) 

Geometry - The Eight Fold Way?

The Jebwatribe constructed Dreamcatchers by tying sinew strands in a web around a small
round or tear-shaped frame of willow, similar to their technique for making snowshoe webbing.
Their designs echo the mandala retino-cortical template, commonly with eight or six vertices.

Flicker , with  a   Strobe- Lamp.

"Toggling briskly between 20−40 f.p.s., some dark and light standing waves appeared with
wavelengths then estimated at 30−300 micron."  

Composite sketch; scale  ~  30 degree angular  subtense.   An  impression of  the  rapidly
expanding focal  wave-fronts;  these  arise  sequentially at progressively eccentric zones,
representing the neural firing- thresholds of cluster/nodes , activated  at varied flicker rates.
At the higher rates, those more centrally appear resonant. Similar configurations are also
seen in the "rose figure" referred to here in Topic D10.